The invention relates to a process and an arrangement for quality monitoring, i.e. a testing of the hermeticity of wafer bond connections as they are e.g. used for the production of MEMS (micoelectromechanical structures) by forming, for instance, glass and silicon wafers for producing hermetically tight cavities, in which the micromechanical sensor element is located. Such sensor elements require a high hermeticity of the cavity since the reliability and service life of the component depend to a high degree on the hermeticity of the wafer connection.
Normally, the procedure is such that in the elaboration of the bonding process by means of special control methods, e.g. by means of infrared microscopy, the hermeticity is tested and, depending on this, the process parameters are optimized. Leakages which may result in the current production operation, will only become apparent much later due to changes in data of the finished components. The discarding of the finished components, however, is a relative expensive process, since quite a number of very expensive and complex process steps had to be used for components which then no longer correspond to the required specifications.
Various processes for the testing of cavities in wafer bond connections have been described in the prior art, which, however, are only conditionally suitable for the testing of cavities under production conditions.
Nese et al., “New method for testing hermeticity of silicon sensor structures”, A 53 (1996), pages 349 to 352, show e.g. a process for assessing semiconductor wafer bonding processes as regards the hermeticity, in which the gas concentration in the hermetically tight cavity of a test chip is measured by means of FTIR spectroscopy (Fourier transform infrared spectroscopy).
DE-B 197 39 961 describes a process for determining the gas pressure in a cavity with deformable walls of a semiconductor component, which is based on a resonance frequency measurement. Moreover, a process is known from DE-A 101 36 219, in which a capacity measurement of the test items immersed in a test liquid under defined conditions is implemented for testing the hermeticity of hermetically tight sensors, the test items having been previously subjected to a vacuum in special cases.
It is the object of the invention to indicate a technique for testing the hermeticity, which results in a safe result within a relative short period of time so that, thus, the testing of the hermeticity can also be used within the framework of a production control in wafer processes.